The present invention relates to an injection molding nozzle and, and more particularly, to a needle assembly for an injection molding nozzle that permits selective, incremental axial adjustment of the gating needle with respect to the face of the mold gate.
In injection molding processes, pressurized molten plastic material, or melt, is directed from a heated nozzle through a gate into a mold cavity. Typically, the front end of the nozzle may include a central gating needle or “torpedo” that extends past the outlet of the nozzle so as to be in proximity to the gate of the mold cavity. The position of the gating needle with respect to the gate affects the way the melt behaves around the gate. For example, the molded product may have a “gate vestige” attached thereto at the gate location. The position of the gating needle can be adjusted to reduce the likelihood of a gate vestige, and thus produce a more cosmetically pleasing appearance for the finished products.
Thus, in setting-up or qualifying an injection molding system for production, it is not uncommon for there to be a need to adjust the positioning of the gating needle with respect to the gate in order to, e.g., effect the flow rate and/or heat transfer at the gate. In addition, after the injection molding system is initially set-up, the gating needle erodes or wears away due to the abrasive nature of the melt or chemical interaction between the melt and the metal comprising the gating needle.
Typically, advancement of the gating needle into the gate has required removing the mold from the machine, disassembling the mold, and grinding the mold, while retraction of the needle has required grinding or filing the gating needle to adjust the extent to which it extends beyond the outlet of the nozzle. As can be readily appreciated, such procedures for making relatively minor adjustments in the position of the gating needle are both inexact and time consuming.
Accordingly, it is an object of the present invention to provide a needle assembly with an adjustable gating needle for an injection molding nozzle.
More specifically, it is an object of the present invention to provide a needle assembly having a gating needle in which the needle may be adjusted without machining or otherwise working the needle or mold plates.
It is also an object of the present invention to provide such an adjustable gating needle assembly where the adjustment may be made selectively and incrementally with a high degree of accuracy.
It is a further object of the invention to provide such a gating needle whose adjustment is achieved simply by disassembly and reassembly of the parts comprising the needle assembly.